1. Field Of The Invention
The present invention is directed to vibratory sealing screens, to filtering screens, to devices with vibrating screens, to shale shakers with vibrating screens, to shale shakers with sealed tiered screens, and to methods and devices for mounting one or more screens in a shale shaker.
2. Description of Related Art
The prior art discloses a wide variety of vibrating screens, devices which use them, shale shakers, and screens for shale shakers. In shale shakers which use a plurality of screens, problems are encountered with the leakage of fluid, e.g. mud, between screens and between screens and the edges of screen supporting members. Mud which leaks through these areas is not screened; i.e. an acceptable level of the separation of liquid (e.g. oil) from cuttings or drilling solids is not achieved.
The need for solids control in drilling mud in hydrocarbon well drilling is well known in the prior art. Drilling mud, typically a mixture of clay and water and various additives, is pumped through a hollow drill string (pipe, drill collar, bit, etc.) down into a well and exits through holes in a drillbit. The mud picks up cuttings (rock bits) and other solids from the well and carries them upwardly away from the bit and out of the well in a space between the well walls and the drill string. At the top of the well, the solids-laden mud is introduced to a shale shaker, a device which typically has a series of screens arranged in tiered or flat disposition with respect to each other. The screens catch and remove solids from the mud as the mud passes through them. If drilled solids are not removed from the mud used during the drilling operation, recirculation of the drilled solids can create viscosity and gel problems in the mud, as well as increasing wear in mud pumps and other mechanical equipment used for drilling. In some shale shakers a fine screen cloth is used with the vibrating screen. The screen may have two or more overlying layers of screen cloth. The frame of the vibrating screen is resiliently suspended or mounted upon a support and is caused to vibrate by a vibrating mechanism, e.g. an unbalanced weight on a rotating shaft connected to the frame. Each screen may be vibrated by vibratory equipment to create a flow of trapped solids in either direction on top surfaces of the screen for removal and disposal of solids. The fineness or coarseness of the mesh of a screen may vary depending upon mud flow rate and the size of the solids to be removed.
Certain prior art screens have sealing members along opposed sides of the screens to seal downwardly against or upwardly against a mounting surface, e.g. a screen mounting member such as a "C" shaped channel. In other prior art devices, the screens are pressed against seals which are disposed on and/or secured to the mounting apparatus; in one device this is done on four sides of a rectangular screen. Applicant is unaware, however, of any prior art which addresses the problem of leakage at ends of channel mountings which hold screens.